Patient treatment for heart conditions often occurs only after an adverse event such as acutely de-compensated heart failure resulting in hospitalization. However, patients may be provided with an implanted medical device (IMD) to monitor for signs of impending de-compensation and other problems. IMDs can also provide electrical pacing therapy to treat impending de-compensation and other problems. IMDs can measure and record electrical cardiac activity, physical motion and other clinical parameters.
The data collected by these devices can be retrieved from the device. In a typical configuration, an IMD is provided with an antenna for communicating by telemetry with a device outside of the patient's body. In one case, the device outside of the patient's body is a wand that is held against or near the patient's body in the vicinity of the implanted device. The wand is conventionally magnetically or inductively coupled to the IMD and is wired to a programmer and recorder module that receives and analyzes the information from the implanted device and that may provide an interface for a person such as a physician to review the information. The programmer and recorder module is in turn connected to a host computer which is monitored by medical professionals.
In other cases, an IMD has far-field RF telemetry capabilities, so that the IMD can communicate with a monitoring unit in the patient's home without requiring any action by the patient. It is not necessary for a patient to place a wand near the implanted device in these systems. The IMD communicates with a repeater located in the patient's home via a far field wireless communications link. For example, one known RF communication system for these short-range distances is the LATITUDE® Advanced Patient Management system sold by Boston Scientific Corporation of St. Paul, Minn. Such a system usually includes a patient monitor device that can receive transmissions from an IMD from within about 9 to 12 feet. In one known arrangement, a patient places a patient monitor device in a living space, such as on a stand next to the patient's bed, so that the patient monitor device can receive data transmitted from the IMD while the patient is in proximity to the monitor device. The patient monitor device is connected to a host computer that is monitored by medical professionals.
While the use of a patient monitor unit is convenient for a patient while located near the repeater, such as within 9 to 12 feet, no data can be transmitted from the implanted device to the repeater if the implanted device is out of range. If a medically significant event occurs while the implanted device is out of range of the repeater, it will not be possible to transmit information about the medically significant event back to the host computer at that time.
IMDs provided to heart failure patients frequently are also capable of electronic signal processing to deliver a medical therapy. One example of a type of implantable medical device is a cardiac rhythm management (CRM) device. CRM devices may include, for example, cardiac resynchronization devices, pacemakers and implantable cardioverter defibrillators (ICD). These devices generally provide medical treatment to a patient having a disorder relating to the pacing of the heart, such as bradycardia or tachycardia. For example, a patient having bradycardia may be fitted with a pacemaker, where the pacemaker is configured to monitor the patient's heart rate and to provide an electrical pacing pulse to the cardiac tissue if the heart fails to naturally produce a heart beat at a sufficient rate. By way of further example, a patient may have an ICD implanted to provide an electrical defibrillation shock to the patient's heart if the patient experiences fibrillation.
IMDs may further be configured to receive instructions from an external source to modify and control the operation of the IMD. For example, a physician may transmit instructions from an external device to an implanted medical device within a patient to change the therapy administered to the patient in response to the physician's analysis of information received about the patient's condition.
Improved systems for communications of signals to and from implantable medical devices are needed, especially while the patient is not in range of a home monitoring unit.